Input variables of yambo_rt

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Input variables of yambo_rt

Postby shenchenhai » Mon Feb 25, 2019 11:34 am

Dear developer,
I would like to know how to calculate the linear-response in real-time for materials. When I use the command yambo_rt -u -F input_rt.in to generate the input. I am not quite sure what the physical meaning of some variables in the input file is and what the given optional values represent. These variable names are as follows.

% Field1_Freq
0.00 | 0.00 | eV # [RT Field1] Frequency
%
Field1_DFreq= 0.000000 eV # [RT Field1] Frequency step
Field1_Int= 0.000000 kWLm2 # [RT Field1] Intensity
Field1_Width= 0.000000 fs # [RT Field1] Width
Field1_FWHM= 0.000000 fs # [RT Field1] Full Width at Half Maximum (alternative to Width)
Field1_kind= "none" # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)
Field1_pol= "none" # [RT Field1] Pol(linear|circular)
% Field1_Dir
1.000000 | 0.000000 | 0.000000 | # [RT Field1] Versor
%
% Field1_Dir_circ
0.000000 | 1.000000 | 0.000000 | # [RT Field1] Versor_circ
%
Field1_Tstart= 0.000000fs # [RT Field1] Initial Time

Can you give me a description of these variables, or where can I find the learning materials about them?
Thank you for your help.

Yours sincerely
Chenhai Shen
Chenhai Shen
Department of Physics, Henan Normal University
Xinxiang, 453000
shenchenhai
 
Posts: 12
Joined: Thu Mar 29, 2018 11:41 pm

Re: Input variables of yambo_rt

Postby Davide Sangalli » Mon Feb 25, 2019 11:53 am

Dear Chenhai Shen,
you need to set:

Code: Select all
Field1_kind= "DELTA" # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)
Field1_pol= "linear" # [RT Field1] Pol(linear|circular)


and a small value for
Code: Select all
Field1_Int= 0.000000 kWLm2 # [RT Field1] Intensity

What is "small" depends on the system. You can try with 1.E4 for a start.

Moreover
Code: Select all
% Field1_Dir
1.000000 | 0.000000 | 0.000000 | # [RT Field1] Versor
%

defines the direction along which the dielectric function is computed.
Setting the "x" direction as above, ypp_rt will then reconstruct eps_{xi} with i={x,y,z}

You should also see variables which define the number of bands included in the calculation and the kind of approximation you would like to use.
Few info can be found here (section VII):
https://arxiv.org/abs/1902.03837

Best,
D.
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.ism.cnr.it/en/davide-sangalli-cv/
http://www.max-centre.eu/
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Re: Input variables of yambo_rt

Postby shenchenhai » Fri Mar 15, 2019 3:28 pm

Thank you very much for your reply, I also want to know how to calculate the real-time spectrum when the incident light is linearly polarized or circularly polarized. Can you give me some help?
Chenhai Shen
Department of Physics, Henan Normal University
Xinxiang, 453000
shenchenhai
 
Posts: 12
Joined: Thu Mar 29, 2018 11:41 pm

Re: Input variables of yambo_rt

Postby Davide Sangalli » Mon Mar 18, 2019 9:48 am

Dear Chenhai Shen,
following the indication in the previous message you will be able to reconstruct the absorption spectrum when light is linearly polarized.
Just run as a first step
Code: Select all
yambo_rt -n p -v sex

and then
Code: Select all
ypp_rt -t X


On the other hand you can run simulations with circularly polarized light.
You just need to set

Code: Select all
Field1_pol= "circular" # [RT Field1] Pol(linear|circular)

and

Code: Select all
% Field1_Dir
 1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
 0.000000 | 1.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

for a field circularly polarized in the xy plane.
However we did not code yet the expression to reconstruct the absorption spectrum.
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.ism.cnr.it/en/davide-sangalli-cv/
http://www.max-centre.eu/
User avatar
Davide Sangalli
 
Posts: 315
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Location: Via Salaria Km 29.3, CP 10, 00016, Monterotondo Stazione, Italy

Re: Input variables of yambo_rt

Postby shenchenhai » Sun Mar 31, 2019 5:33 am

Thank you very much for your reply. I still have a few questions that are not too clear.
1.Field1_Width= 0.000000 fs # [RT Field1] Width
What is the physical meaning of this parameter and how should it be set?

2.Field1_kind= "DELTA" # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)
How to set this parameter when calculating circularly polarized light?

3.How to set the left and right circularly polarized light, separately?

Can you give me some help?
Chenhai Shen
Department of Physics, Henan Normal University
Xinxiang, 453000
shenchenhai
 
Posts: 12
Joined: Thu Mar 29, 2018 11:41 pm

Re: Input variables of yambo_rt

Postby Davide Sangalli » Mon Apr 01, 2019 9:54 am

1.
Code: Select all
Field1_Width= 0.000000 fs # [RT Field1] Width

What is the physical meaning of this parameter and how should it be set?


It is the pulse duration in case you select "GAUSS" or "QSSIN" in point 2

Code: Select all
Field1_kind= "DELTA" # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)

How to set this parameter when calculating circularly polarized light?


It is the kind if pulse in the simulation.
- "DELTA" is a "Dirac Delta in time" pulse and is usually what you want to compute absorption
- "SIN", "RES" and "ANTIRES" are pulses which oscillate in time at a specific frequency
- "GAUSS" is a gaussian in time
- "QSSIN" is a pulse with a Gaussian profile in time, convoluted with a function oscillating at a specific frequency

The circular polarization is constructed using two linearly polarized pulses shifted in time by T/4 (here T=2pi/omega is the period)
It is meaningful only for the pulses where a frequency is defined: "SIN", "RES" "ANTIRES", "QSSIN"
It is ignored otherwise


3.How to set the left and right circularly polarized light, separately?

One option is to set for left
Code: Select all
% Field1_Dir
  1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
  0.000000 | 1.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

and for right
Code: Select all
% Field1_Dir
  1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
  0.000000 | -1.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

or
Code: Select all
% Field1_Dir
  0.000000 | 1.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
  1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

(I could have reversed left and right, please check)
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
http://www.ism.cnr.it/en/davide-sangalli-cv/
http://www.max-centre.eu/
User avatar
Davide Sangalli
 
Posts: 315
Joined: Tue May 29, 2012 4:49 pm
Location: Via Salaria Km 29.3, CP 10, 00016, Monterotondo Stazione, Italy

Re: Input variables of yambo_rt

Postby shenchenhai » Tue Apr 02, 2019 1:16 pm

Thank you very much for your reply!
Suppose I want to calculate the absorption spectrum of left-handed circularly polarized light with an energy ranging from 0 to 5 eV. Are the following parameters correct?

% Field1_Freq
0.00 | 5.00 | eV # [RT Field1] Frequency
%
Field1_DFreq= 0.020000 eV # [RT Field1] Frequency step
Field1_Int= 10000.000000 kWLm2 # [RT Field1] Intensity
Field1_Width= 0.000000 fs # [RT Field1] Width
Field1_FWHM= 0.000000 fs # [RT Field1] Full Width at Half Maximum (alternative to Width)
Field1_kind= "SIN" # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)
Field1_pol= "circular" # [RT Field1] Pol(linear|circular)
% Field1_Dir
1.000000 | 0.000000 | 0.000000 | # [RT Field1] Versor
%
% Field1_Dir_circ
0.000000 | 1.000000 | 0.000000 | # [RT Field1] Versor_circ
%
Field1_Tstart= 0.000000fs # [RT Field1] Initial Time

If this is not correct, What should the correct Settings be?
Chenhai Shen
Department of Physics, Henan Normal University
Xinxiang, 453000
shenchenhai
 
Posts: 12
Joined: Thu Mar 29, 2018 11:41 pm


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